Columns used in liquid chromatography typically comprise a body-forming structure enclosing a porous media through which a carrier liquid flows, with separation taking place by material collection between the carrier liquid and solid phase of the porous media. Typically, the porous media is enclosed in the column as a packed bed, typically formed by consolidating a suspension of discrete particles. An alternative to the packed bed is the so-called expanded or fluidised bed, where effective porosity and volume of the expanded bed depends on the fluid velocity. The term ‘bed’ shall be used in the following to describe the porous solid phase in all types of chromatography. The efficiency of the chromatographic separation relies in both modes strongly on the liquid distribution and collection system at the fluid inlet and outlet of the packed bed, and on the homogeneity of the packed bed.
Prior to any separation process, the bed has to be prepared starting from a suspension of particles that has to be introduced into the column. The process of bed formation is called ‘packing procedure’ and is especially critical for packed beds. The goal of this procedure is to provide a bed of ideal homogeneity. Large scale columns are preferably prepared by injecting a slurry of media particles through a central slurry nozzle. The excess liquid during this procedure is removed at the column outlet, while the particles are retained by means of a filter material, a so-called ‘bed support’. The process is complete once the packed bed has completely filled the chromatographic column. The packing process is considered as being successful if the homogeneity and stability of the packed bed allows for a good and robust chromatographic performance quantified in terms of the residence time distribution over the bed. However, if an attempt is made to pack an empty column with bed media using such a slurry nozzle and the bed height is small compared to the column width, then the packing efficiency and bed homogeneity is low. The fluid dynamics of the suspension phase becomes unfavourable such that particles are not distributed and deposited evenly across bed interface. Literally speaking, the jet of suspension leaving the nozzle is not strong enough to transport bed media all the way to the column walls, especially toward the end of the process when the bed interface is in vicinity of the top adapter confining the column at the inlet side. As a result, the bed interface grows with a non-uniform growth rate leading to an uneven bed interface with the maximum height of the interface occurring at a radius smaller than the perimeter of the bed.
Co-pending patent applications GB 0111485.9 and GB0111486.7 describe chromatography devices in which the liquid distribution at the inlet side of the column is achieved by first distributing the liquid radially through one or more horizontal collection slots and then allowing the liquid to enter the column though one or more annular slits arranged intermediate the centre of the column and the wall of the column. A similar liquid collection arrangement is used at the outlet end to collect the liquid leaving the column. Such a liquid collection system is also in operation for removing excess liquid during the packing process and object of the invention.
As used herein and in the appended claims: the term “fluid system” is intended to designate the apparatus in which liquid is either introduced to or withdrawn from a cell at a zone approximately transverse the direction of flow through the cell. The term “cell” is intended to include the terms “vessel” and “column”, as well as any other structure utilised by practitioners of the separation arts, to effect a separation, and/or reaction, and/or catalysation and/or extraction of components from an admixture by bringing the admixture into contact with solid or liquid exchange media, above referred to as the packed bed, and/or for the purpose of sintering/consolidating bed material to form a bed, for example a monolithic bed. “Cross-sectional zone” (or region) refers to a region within a cell bounded by cross sections of the cell-oriented transverse (typically approximately normal) the longitudinal direction of flow through the cell. “Longitudinal direction of flow” refers to the direction of flow from an inlet towards an outlet within a cell. “Longitudinal” is used consistently to designate the dominant flow path of fluid through a cell without regard to direction. “Flow connection system” refers to a system of channels or paths that connect two points in a fluid circuit. “Collection system” refers to structures through which fluids are introduced to a cell and “collection system” refers to structures used to withdraw fluids from a cell, in each instance from a cross-sectional zone.